Narrated Abu Sa`id: The Prophet saw sputum on (the wall of) the mosque in the direction of the Qibla and scraped it off with gravel. Then he forbade Spitting in front or on the right, but allowed it on one's left or under one's left foot.
Hadith ReferenceSahih Bukhari / The Book of As-Salat (The Prayer) / Hadith: 414
Hadith Gradingمحدثین:أحاديث صحيح البخاريّ كلّها صحيحة